1. Field of the Invention
The present invention generally relates to molding machines, and more particularly, to a molding machine having a movable mold support apparatus.
2. Description of the Related Art
Generally, there is an injection molding machine, a die-cast machine, an injection sealing press machine or the like in molding machines. For example, in the injection molding machine, resin heated and melted in a heating cylinder is injected into a cavity of a mold apparatus under high pressure so that the cavity is filled with the molten resin. The molten resin is then cooled and solidified so as to obtain a molded article.
The mold apparatus is provided with a stationary mold and a movable mold. The movable mold is advanced and retracted by a mold clamping apparatus, to thereby perform mold closing, mold clamping and mold opening.
The mold clamping apparatus is generally provided with a stationary platen supporting the stationary mold and a movable platen supporting the movable mold.
A toggle mechanism is disposed in the mold clamping apparatus to advance or retract the movable platen and perform the opening and closing of the mold.
The toggle mechanism is operated by driving with an electric motor, a servo motor or the like disposed in a driving part.
FIG. 1 is a first sectional view of a movable platen of a related art injection molding machine. FIG. 2 is a second sectional view of the movable platen of the related art injection molding machine.
Referring to FIG. 1 and FIG. 2, a movable platen 100 includes a plurality of tie bars 107, for example four tie bars. The tie bars 107 are disposed between a stationary platen and a toggle support not shown in FIGS. 1 and 2. The movable platen 100 is disposed as facing the stationary platen and being capable of advancing or retracting (moving rightward and leftward in FIG. 2) along the tie bars 107.
A stationary mold not shown in FIGS. 1 and 2 is disposed on a mold mounting surface of the stationary platen facing the movable platen 100. A movable mold 105 is disposed on a mold mounting surface 110 of a mold mounting plate 101 of the movable platen 100 facing the stationary platen.
A first load receiving part 102 and a second load receiving part 103 are formed at a rear surface, namely a surface opposite the mold mounting surface 110 of the mold mounting plate 101. The first load receiving part 102 has a first pin inserting hole 111 for inserting a toggle pin of an upper side of the toggle mechanism not shown. The second load receiving part 103 has a second pin inserting hole 114 for inserting a toggle pin of a lower side of the toggle mechanism not shown.
The first load receiving part 102 and the second load receiving part 103 are members made of high strength material so that the first load receiving part 102 and the second load receiving part 103 can receive a mold closing force and a mold clamping force for moving the movable platen 100 rightward in FIGS. 1 and 2 by the toggle mechanism. Hence, the first load receiving part 102 and the second load receiving part 103 are formed with the mold mounting plate 101 in a body.
Furthermore, the same number of guide parts 104 each having a guide hole 106 as the number of tie bars 107 are provided at the movable platen 100. The tie bar 107 is inserted into the guide hole 106. A bush 108 which can slide against the tie bar 107 is inserted in each of the guide holes 106. Grease as a lubricant material is received in a gap between the guide hole 106 and the tie bar 107.
When the movable platen 100 is moved forward (rightward in FIG. 2) by the toggle mechanism not shown in FIG. 2, the movable mold 105 is pushed against the stationary mold not shown in FIG. 2 so that mold closing and mold clamping are performed.
The toggle mechanism is disposed to the rearward (leftward in FIG. 2) of the movable platen 100. The toggle mechanism generally includes a toggle lever supported as being capable of swinging against the cross head, another toggle lever supported as being capable of swinging against the toggle support, and a toggle arm supported as being capable of swinging against the movable platen. The toggle lever and the toggle arm are link-connected. The mold clamping force is transmitted to the first load receiving part 102 and the second load receiving part 103 of the movable platen 100 by the above mentioned toggle mechanism. Here, a driving force generated by a driving part such as a motor is multiplied by a toggle ratio, so that the mold clamping force is calculated.
However, the above mentioned and related injection molding machines have the following problems.
Firstly, when the first load receiving part 102 and the second load receiving part 103 receive a strong force from the toggle mechanism for mold clamping and mold closing, the mold mounting plate 101 is bent. As a result, the mold mounting surface 110 of the mold mounting plate 101 may be deformed.
As shown in FIG. 1, the first load receiving part 102 is disposed at the opposite side and higher than the movable mold 105. The second receiving part 103 is disposed at the opposite side and lower than the movable mold 105. FIG. 1 shows a state where the movable mold 105 is pushed to contact the stationary mold not shown in FIG. 1 so that the movable mold 105 cannot be moved. Accordingly, when the first load receiving part 102 and the second load receiving part 103 receive a strong and rightward force from the toggle mechanism, a bending moment is applied to the mold mounting plate 101.
As a result, the mold mounting plate 101 is bent and deformed as shown by one point doted lines in FIG. 1. Therefore, the mold mounting surface 110 is also deformed as shown by additional one point doted lines. Thus, when the mold mounting surface 110 is deformed as shown by additional one point doted line, the movable mold 105 is deformed so that the quality of the molded article is reduced. The deformations of the mold mounting plate 101 and the mounting surface 110 shown in FIG. 1 are drawn with exaggeration in order to explain the deformations.
In order to prevent the mold mounting plate 101 and the mounting surface 110 from deforming, it was attempted in the related art injection molding machine to increase the thickness of the mold mounting plate 101 so that a rigidness of the mold mounting plate 101 would be improved.
However, if the thickness of the mold mounting plate 101 becomes greater, the cost for manufacturing the movable platen 100 becomes high. Furthermore, in this related art case, it is necessary to improve the strength of the entire injection molding machine because weight of the movable platen 100 increases. Therefore, the cost for manufacturing of the entire injection molding machine may become high.
Secondly, in the above mentioned and related art injection molding machines, grease leaking out from the gap between an inner circumferential surface of the bush 108 and an outer circumferential surface of the tie bar 107 may flow downward as shown by an arrow 109. As a result of this, the grease may adhere to the mounting surface 110 or the movable mold 105.
That is to say, as shown in FIG. 2, the grease received in the gap between the guide hole 106 of the guide part 104 and the tie bar 107 may leak out from the gap between the inner circumferential surface of the bush 108 and the outer circumferential surface of the tie bar 107. In this case, if the grease leaks out at the rear surface side of the mold mounting plate 101 and flows downward, the grease drops down without adhering to the mold mounting surface 111 or the movable mold 105. Hence, the above mentioned leaking out of the grease may not be a problem.
However, the grease leaking out to the side of the mold mounting surface 110 adheres to a wide area of the mold mounting surface 110. Hence, there is an extremely high probability that the grease adheres to the movable mold 105. If the grease adhering to the mold mounting surface 110 and the movable mold 105 adheres to the molded article, the quality of the molded article declines. Therefore, the rate of producing low quality molded articles may become high in the above mentioned related art injection molding machine.